League of Legends random black screens when freesync is turned on

I get random black screens in League of Legends when Freesync is turned on, whenever i turn it off the black screens stop to appear . The sound keeps playing and they last about 2 seconds but i can continue playing after the black screen disappears but is really annoying in a such a fast paced game. And its a shame of loosing the smoothness of freesync just because of these issues. I already messaged the support of the game but they couldnt really help me so i guess it must a driver issue. I already switched cables using HDMI and Displayport and there was no difference. Plus i dont hear any disconnecting sounds just the normal ingame sound and i can still hear my mates in Discord.

So i hope u can help me here to fix this very annoying Problem which i hope im not the only one with

EDIT: the black screens still appear even tho freesync is disabled .....